We need to know what the coordinates of 'X' were BEFORE the reflection.
The only information you've given us so far is the reflection line
and the names of the triangle's vertices.
The point (1, -3) is 4 units below the line y=1.
If you flop it across that line, it winds up 4 units above y=1.
Then it's located at
(1, 5) <===
